Biomass is an abundant potential source of fuels and specialty chemicals. Any kind of biomass can be used to extract carbohydrates, proteins, fats, and other valuable compounds, but, in particular, the carbohydrate polymers of biomass derived from plants, algae or microorganisms are used to produce such products. Biomass generally includes three main structural elements: lignin, hemicellulose, and cellulose. Certain components (e.g., lignin) can reduce the chemical and physical accessibility of cellulose and hemicellulose, which in turn, reduces the susceptibility of these carbohydrate polymers to chemical and/or enzymatic conversion. Because of differences in the bonding of compounds in biomass and because of the presence of the lignin sheath, it can be more difficult to process the cellulose and hemicellulose in biomass than it is to process the starches in grains. Yet, in order to avoid the use of food crops, bioenergy facilities are being promoted that utilize the human inedible portions of biomass.
Many of the methods used to make the hemicellulose and cellulose of biomass more accessible can generate inhibitor compounds that can negatively affect downstream processing, such as saccharification and/or fermentation. There is a need for pretreatment process that provides a biomass fraction that is accessible to effective enzymatic hydrolysis without the formation or release of large volumes of inhibitors.